This invention relates to the treatment of highly olefinic gasoline containing at least about 50% by weight of olefins by contacting said olefinic gasoline with a special group of acidic crystalline aluminosilicate zeolites, such as those of the ZSM-5 type in order to enhance to gum stability of said gasoline and produce products comprising both gasoline and fuel oil.
There are many processes known in the patent and technical literature which produce olefinic gasolines having an olefin content of at least 50 weight percent, such as U.S. Pat. No. 3,960,978. Thus, by way of illustration, fluid catalytic cracking processes produce a light olefin product stream which when charged over ZSM-5 as "wet" gas results in olefinic gasoline. The "wet" gas comes from a piece of equipment called an accumulator which is before the gas plant compressor. A more recent process resulting in the production of olefinic gasolines involves contacting synthesis gas over iron or cobalt ZSM-5 type compositions under certain conditions. This process is believed to go through a light olefin intermediate (Journal of Catalysis, Vol. 56, 274, 1979).
These olefinic gasolines have good unleaded research octane numbers of 90 and higher, but unfortunately also have poor gum stability. In addition, reaction constraints in both systems, i.e. the petroleum route and the synthesis gas route, limit the liquid product essentially to gasoline. In some situations, especially in those areas of the world that are short of petroleum, the synthesis gas route might be attractive and it would be advantageous to produce both gasoline and fuel oil products such as diesel fuel, home heating oils, jet fuel, etc.